Field of the Invention
The present invention relates to a broach in which a plurality of cutting edges are formed on a broach body. The cutting edges of the broach are inserted, together with the broach body, into a prepared hole formed in a work material, in order, to form the prepared hole in a predetermined shape such as an internal gear shape using grooving or machining of the inner circumference.
Priority is claimed on Japanese Patent Application No. 2013-070820, filed on Mar. 29, 2013, the content of which is incorporated herein by reference.
Description of Related Art
As such a broach of the related art, there is known a broach that is provided with a shaft-shaped broach body and a plurality of cutting edges that are arranged on an outer circumference of the broach body spaced apart at intervals in an axial direction of the broach body. The broach body is inserted into a prepared hole that is formed in the work material facing a tool feed direction along the axial direction. At this time, the plurality of cutting edges groove the prepared hole and machine the inner circumference of the prepared hole, thereby cutting the prepared hole into a predetermined shape such as an internal gear shape.
For example, in the helical broach disclosed in Japanese Patent No. 3377713, the broach body is of an assembly type in which the broach body is configured to have a shaft-shaped body section, which includes a larger-diameter section and a smaller-diameter section that are adjacent to one another in the axial direction, and a cylindrical shell section. The shell section is mounted in a removable manner onto the smaller-diameter section that is positioned on a rear portion of the body section. In a state in which the body section and the shell section are assembled, the plurality of cutting edges form rows along the outer circumference of the larger-diameter section and the outer circumference of the shell section in the body section.
The cutting edges are provided with a spline teeth group, which contains a plurality of spline teeth that groove a prepared hole of the work material, and a round teeth group, which contains a plurality of round teeth that machine the inner circumference of the prepared hole. In the case of a broach with rear round teeth, the round teeth group is entirely disposed on the shell section, closer to the rear in the tool feed direction than the spline teeth group.
With such a broach with rear round teeth, it is possible to reduce the interval between cutting edges (between the spline teeth or between the round teeth) of the same type that are adjacent to one another in the axial direction in comparison to an alternate round teeth type of broach (a broach in which the spline teeth and the round teeth are disposed alternately in the axial direction). In particular, even when the length of the work material along the axial direction is short (that is, the thickness of the work material is thin), it is possible to cause a plurality of the spline teeth or the round teeth to cut into the prepared hole at a time, and the broach can be widely adapted for various work materials.